HMG-14 and HMG-17 are ubiquitous non-histone chromosomal proteins that bind to nucleosome core particles. They form a family of chromosomal proteins that have been reported to bind active chromatin. To understand the in vivo function of these proteins, we disrupted both HMG-14a and HMG-17 in an avian B-cell line DT40. Our results indicate that the knockout cells show no obvious change in phenotype with respect to the parental DT40 cells. Furthermore, no compensatory changes in HMG-14b or histone protein levels were observed in cells lacking both HMG-14a and HMG-17. Upon 2-D gel electrophoretic analysis, a major expresssed protein was found to be activated in the knockout cells. Developing methods for analyzing proteins in gels and directly on transfer membranes are being employed to identify this particular spot.